Control valves are commonly used in process control systems to control the flow of process fluids. A control valve typically includes an actuator (e.g., a pneumatic actuator, a hydraulic actuator, etc.) operatively coupled to a flow control member to automate the control valve. In operation, a control fluid (e.g., air) is supplied to the actuator to position the flow control member relative to a valve seat to regulate fluid flow through the control valve.
Many process control applications require actuators (e.g., valve actuators) to include fail-safe systems. A fail-safe system provides protection to a process control system by causing the actuator and, thus, the flow control member to move to either a fully-closed position or a fully-opened position during emergency situations, power failures, and/or if the control fluid (e.g., air) supply to an actuator (e.g., a pneumatic actuator) is shut down.
To provide a fail-safe system, some actuators include a biasing member disposed in a cylinder of the actuator. However, in some instances, including a biasing member may significantly increase a dimensional envelope (e.g., length) of the actuator. In other instances, including a biasing member may require complex assembly or tools if the cylinder of the actuator has a smaller dimensional length than the biasing element.